Manufacture of tubing and clad rods or wire



K. B. CLARK 3,355,795

TUBING AND AD R DS 0 2 Sheets-Sheet 1 K. B. CLARK 3,355,195

MANUFACTURE OF TUBING AND CLAD RODS OR WIRE Dec. 5, 1967 2 Sheets-Sheet2 Filed June 10, 1964 FIGS.

FIGS.

United States Patent ()fifice 3,355,795 Patented Dec. 5, 1967 3,355,795MANUFACTURE OF TUBING AND CLAD RODS OR WIRE Kenneth B. Clark,Spragueville, R.I., assignor to Texas Instruments Incorporated, Dallas,Tex., a corporation of Delaware Filed June 10, 1964, Ser. No. 374,023 2Claims. (Cl. 29-481) ABSTRACT OF THE DISCLOSURE Tubing, clad rods, wiresand the like are manufactured in a continuous operation from hard-metalstrip material bent to form a cylinder and edge-bonded in the solidphase by rolling. This involves the formation of certain fins with goodbonding in the fin regions but weaker bonding interiorly of the fins.Heretofore the fins have been eliminated by skiving or drawing of thecylinders which removed or damaged the best bonded edge portions anddamaged the weaker interior bonds. According to the invention, prior toskiving or drawing, the cylinders are subjected to substantial sinteringbefore rather than after such fin elimination, which strengthens theweak interior bonds so as to be proof against the damaging effects ofthe skiving which removes the fins. The bending, bonding, sintering andfin elimination occur in a single pass. By this means, which may becarried out in a rapid continuous process, the initially weak innerportions of the solid-phase bonds, as rolled, can be effectivelyimproved by the sintering, rather than having such weak portions sodamaged by premature skiving or drawing operation that the sinteringwould be incapable of adequately improving the bonds.

Among the several objects of the invention may be noted the provision ofimproved means for the manufacture of tubing and clad rods, wires andthe like which are made from bonded sheets formed as cylinders or thelike; the provision of means of the class described according to whichbonded fins which are a concomitant of sheet-to-sheet bonds can beremoved without substantially producing an inferior product; and theprovision of means of the class described which may be easily car riedout at low cost. Other objects and features will be in part apparent andin part pointed out hereinafter.

The invention accordingly comprises the ingredients and combinations ofingredients, the proportions thereof, steps and sequencec of steps, andfeatures of composition and manipulation which will be exemplified inthe products and methods hereinafter described, and the scope of theapplication of which will be indicated in the following claims. I I

In the accompanying drawings, in which several of various possibleembodiments of the invention are illustrated,

FIG. 1 is a diagrammatic view illustrating one form of the invention;

FIG. 2 is a view similar to FIG. 1, showing said form of the inventionin finished condition;

FIG. 3 is a view similar to FIG. 1, showing a second form of theinvention;

FIG. 4 is a view similar to FIG. 3, showing said second form in finishedcondition;

FIG. 5 is a view illustrating certain apparatus for making a clad rod orwire such as shown in FIGS. 1 and 2;

FIG. 6 is a view similar to FIG. 5, showing apparatus for making a tubesuch as shown in FIGS. 3 and 4;

FIG. 7 is a cross-sectional view illustrating certain skiving apparatus;and

FIG. 8 is a section taken on line 8-8 of the skiving apparatus of FIG.7.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawmgs.

Hereinafter the terms clad rod and clad wire are to be taken assynonymous, their difference being one of size primarily. The term metalmeans any deformable or malleable metal, including alloys. The termsolid-phase green bond as used herein means a bond made under conditionssuch as set forth in US. Patents 2,691,815 and 2,753,623, and in mostcases preferably the latter.

My two copending United States patent applications, Ser. No. 63,678,filed Oct. 19, 1960, entitled Forming and Solid-Phase Bonding, and Ser.No. 93,513, filed Mar. 6, 1961, entitled Manufacture of Clad Rods,Tubing and Clad Tubing, disclose methods for manufacturing tubes, cladrods and clad wires by transversely bending strips of metal to formcylinders and solid-phase bonding the margins of the strips. Ser. Nos.63,678 and 93,513 have eventuated as US. Patents Nos. 3,220,106 and3,220,107, respectively. In the case of clad rod and wire, the sheetsare bent around a core and, in addition to bonding the strip margins,the strips may also be bonded to the core material. In all cases,sheet-to-sheet connections are made by squeezing under sufficientpressure to obtain a deformation of properly cleaned surfaces sufiicientto bring about solid metal flow and a solid-phase green bond. Thebonding operation results in fins which in most cases require removal.It is in connection with this removal that problems occur and which aresolved by means of the present invention.

Referring now more particularly to FIG. 1, there is shown at numeral 1 acylindrical metallic core clad by metallic sheets 2 and 3 of strip form,the latter having been solid-phase bonded to the core by passage throughsuitable grooved and beaded bending and squeezing rolls R (FIG. 5) andas set forth in said applications. Their grooves are shown at G andtheir beads at B. Solid-phase green bonding occurs between the core 1and the sheets 2 and 3, and also at the pinch caused by the beads B ofthe rolls R. The pinch effect causes. green-bonded fin portions 4. Inthis case a green-bonded clad rod wire results.

If, as shown in FIG. 3, the core 1 is omitted and the sheets 2 and 3 arebent over a suitable mandrel M (FIG. 6) extending between the rolls R,then the flanges F of rolls again squeeze and form fin portions 4. Inthis case a green-bonded tube will result. Like letters and numeralsdesignate like parts in FIGS. 5 and 6 and in FIGS. 1 and 3, only thecore 1 of FIG 1 being missing in FIG. 3. In each of FIGS. 2 and 4 thebent strips 2 and 4 form a metal cylinder which is empty in FIG. 4 butinfilled by the core 1 in FIG. 2.

In general, it is desirable that the fin portions 4 be removed, as byskiving, drawing or the like. For example, skiving is accomplished asshown in FIGS. 7 and 8. The skiving apparatus may consist of a pair ofV-shaped guide wheels W, flanked by the skiving blades S. It has beenthe practice heretofore to skive off the fin portions 4 immediatelyafter the solid-phase green-bonding operation, for example, simply byfeeding the solid-phase, green-bonded material from the squeezing rollsR to the skiving apparatus W, S. This process has been found to besatisfactory in cases in which the sheets 2 and 3 were composed of softmaterial, for example, gold. These bond readily across the entireinterface within the fins 4.

I have found, however, that difiiculties occur when the sheet materialis comparatively hard for forming the cladding (FIG. 1) or the tubing(FIG. 3), such as, for example, nickel, stainless steel or Monel, and incases in which solid-phase green-bonding temperatures are low. Thesedifficulties arise in both the clad rod and tube forms of FIGS. 1 and 3,and more likely in the latter case. The difficulties reside in thefollowing (referring to FIGS.

1 and 3) In the case of hard materials, the weakest solid-phasegreen-bonding occurs in the region of the short heavy solid black lines5, which is to say, at the inside of the fin junctions formed by thesheets 2 and 3. Outside of these lines, there is generally sufficientdeformation accomplished during squeezing to bring about a comparativelystrong green bond. In the case of soft materials for the sheets 2 and 3,the comparatively poorly bonded black-line portion is minimal ornonexistent. The harder the material of which sheets 2 and 3 arecomposed, the greater the extent of the portion indicated by the solidline 5.

Past practice has been to remove all or a substantial portion of thefins 4- by skiving, This removes the portion most likely to be bettergreen-bonded. The removal of the fins at this stage may also damage thecomparatively weak green bond which exists in the region 5. This damagesometimes is so severe that subsequent operations designed to improvethe strength of the green bond are ineffective to improve its strengthat all.

It will be understood that in general solid-phase green bonds aresubsequently sintered to increase their strength to useful values infinished products. Such sintering has heretofore been carried out afterthe skiving operation above-mentioned.

I solve the above-mentioned difficulties by performing the sinteringstep at a time occurring between the roll squeezing step (FIGS. 5 or 6)and the skiving step (FIGS. 7 and 8). This has the effect ofsubstantially increasing the bond strength in region 5. A strong bond isthereby obtained before fin removal throughout substantially the entiredistance, or at least a very large portion of it, extending from theapex of each fin 4 inwardly to the inner cylindrical surface of the tubeformed by the sheets 2 and. 3. This is true in both the cases shown in.FIGS. 1, 2 and FIGS. 3, 4.

An additional feature of the invention is that the intermediatesintering step shall be carried out at higher sintering temperaturesthan are generally employed for the purpose. The higher sinteringtemperatures permit very rapid difiusion across the zone line 5, withrapid growth of the weak green bond into a strong bond across theinterface between the sheet margins so that fin removal may beaccomplished soon thereafter. Heretofore, in the case of nickel, Monelmild steel, some stainless steels and the like employed for the sheetsuch as 2 and 3, a normal sintering temperature would have been in therange of 1100 F.-l400 F. According to the present invention, a highsintering temperature of 1500 F.-280() F. would be employed. It will benoted that in no event may the upper temperature exceed the lowestmelting point of the metals employed as cladding or core materials. Atsuch sintering temperatures, 90% of the full sintered bond strength maybe obtained within a few seconds.

It will be observed in FIGS. 2 and 4 that skiving has been accomplishedso as to leave substantially no exterior evidence of a fin or the like.A slight curvature of the skiving blades may be desirable for thispurpose. It is to be understood that fins may also be removed orobliterated by a drawing operation, rather than or in addition toskiving, if desired. The terms removing or obliterating as applied toelimination of the fins 4 are to be taken as equivalents. The finishedproducts (FIGS. 2 and 4) are of improved final strength, giving nosubstantial evidence of any discontinuity at the junctions between thebonded marginal interfaces of the strips 2 and 3 and presenting littleor no evidence of any exterior protrusion where the fins have beenremoved or obliterated. The short lines transverse to the cross hatchingin FIGS. 2 and 4 show where the improved bond lines are located but inpractice they are hardly detectable microscopically, being quite freefrom inclusions, voids, etc., and therefore strong.

While the core 1 has been illustrated as being solid, it will beunderstood that it may itself consist of a tube, so that instead ofobtaining a clad rod as illustrated in FIG. 2., a clad tube would beobtained.

It will be understood that the provision of the hightemperaturesintering between the steps of solid-phase green bonding by rolls on theone hand, and the elimination of the fin portions by skiving or drawingon the other had, have the advantage that all operations can in a singlepass be rapidly performed by a continuous rapid movement of the stripand core materials successively through the bonding rolls, then througha suitable furnace or other heating means, forming a high-temperaturesintering, and finally moving the sintered material through skivingapparatus or drawing dies, without pause between operations.

It will be seen that one feature of the invention is the timing of thesintering step after the squeezing step and before the skiving step; andanother preferable subsidiary feature is the employment of an unusuallyhigh sintering temperature. It is to be understood, however, that lowersintering temperatures may be employed but that they require longersintering times.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above prodnets and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:

1. The method of forming a well-bonded hard-metal cylinder without finscomprising transversely bendingby rolling at least one clean hard-metalstrip to bring to gether margins thereof. and by said rolling effectinga squeezing together of said margins to green-bond the margins in thesolid phase to form the cylinder with at least one fin wherein the bestbondingis in the fin and a weaker bond occurs interiorly of the regionof the fin, subjecting the finned green-bonded cylinder to heating at asintering temperature to improve the interior weaker bond in the solidphase, and thereafter mechanically eliminating the fin. from thecylinder.

2. The continuous single-pass method of forming a well-bonded hard-metalcylinder without fins comprising continuously moving and transverselybending by rolling at least one clean hard-metal strip to bring togethermargins thereof and' by said rolling effecting squeezing together ofsaid margins to green-bond the margins in the solid phase to form thecylinder with at least one fin wherein the best bonding is in the finregion and a weaker bond occurs interiorly of the region of the fin,continuously passing the finned green-bonded cylinder through a heatedspace at a sintering temperature of 1500 F. or more for a few seconds toimprove the interior weaker bond in the solid phase, and thereaftercontinuously passing the sintered cylinder through mechanical means foreliminating the fin from the moving cylinder.

(References on following page) 6 References Cited 3,220,106 11/1965Clark 29--474.1 X UNITED STATES PATENTS 3,220,107 11/ 1965 Clark 29497.5X

5/1869 Vanstone 29-481 FOREIGN PATENTS Mannesmann 5 Great Britain. 2/1903 Mannesmann 2,9 1 573 JOHN CAMPBELL, Primary Examiner. 7/ 1956Boessenkool et a1. 29-497.5

L. I. WESTFALL, Examiner.

1. THE METHOD OF FORMING A WELL-BONDED HARD-METAL CYLINDRICAL WITHOUTFINS COMPRISING TRANSVERSELY BENDING BY ROLLING AT LEAST ONE CLEANHARD-METAL STRIP TO BRING TOGETHER MARGINS THEREOF AND BY SAID ROLLINGEFFECTING A SQUEEZING TOGETHER OF SAID MARGINS TO GREEN-BOND THE MARGINSIN THE SOLID PHASE TO FORM THE CYLINDER WITH AT LEAST ONE FIN WHEREINTHE BEST BONDING IS IN THE FIN AND A WEAKER BOND OCCURS INTERIORLY OFTHE REGION OF THE FIN, SUBJECTING THE FINNED GREEN-BONDED CYLINDER TOHEATING AT A SINTERING TEMPERATURE TO IMPROVE THE INTERIOR WEAKER BONDIN THE SOLID PHASE, AND THEREAFTER THE INTERIOR WEAKER BOND IN THE FINFROM THE CYLINDER.